This invention relates to an orthopedic implant having a bone contacting surface with pegs angled to facilitate implantation of the implant into a prepared bone surface. More particularly, it relates to a tibial implant which has pegs angled in a medial or lateral direction and also in a posterior direction.
Various orthopedic implants have used angled pegs to help stabilize the component after implantation. Various knee prosthesis, either tibial components or femoral components have short pegs extending perpendicularly to the bone contact surface in the condylar area to provide stability on implantation. Some of these implants include central stems which extend into the prepared marrow canal of a long bone. Short peg-like extensions are then provided in the condylar area to prevent rotation of the implant after implantation. For example, many tibial and femoral components are supplied with long central stems for engaging the medullary canal and pegs extending a short distance into the condylar areas of the knee to prevent rotational movement of the inserted prosthesis.
The problem with stems or pegs which extend generally perpendicular to the bone contacting surface of the implant is that they require a large space so that the implant may be moved into position above holes prepared in the bone surface and then moved towards the bone so that the pegs and stem on the prosthesis can engage the corresponding holes in the prepared bone in a co-axial manner. Obviously, this up and down movement requires a significant amount of room above the prepared joint surface.
It has been found that by angling the pegs, it is possible to reduce the amount of space necessary to implant the prosthesis, such as a tibial or femoral component. In this regard, in the early 1990's, a tibial plateau was provided by Howmedica Inc. which had the pegs on the tibial baseplate angled posteriorly so that the tray itself could be inserted by moving it in an anterior-posterior direction rather than a proximal to distal direction as would be necessary if the pegs were perpendicular to the bone contacting surface.
With respect to glenoid components which are often supplied with pegs for insertion into a prepared scapula, these pegs may be angled in the inferior or superior directions to allow implantation in an up to down or proximal to distal orientation. Such a glenoid component is shown in U.S. Pat. No. 5,593,448 to Nicholas Dong. U.S. Pat. No. 4,986,883 to Worland shows a glenoid component having pegs angled posteriorly to facilitate its implantation in an anterior to posterior direction.
It has been found, however, that, especially with the tibia, it is advantageous to implant the prosthetic tray either from a medial-anterior or a lateral-anterior direction or a direct lateral or direct medial direction. This allows the use of a smaller incision than used with the typical anterior-posterior implantation of the tibial tray.